Lamb mulesing: Impact on welfare and alternatives

Abstract

Mulesing is a surgical procedure that is routinely performed without pain relief on Merino and Merino cross sheep to prevent flystrike in the breech region. Pain is apparent immediately following the procedure and persists for at least 2-3 days, and possibly up to 2 weeks, as reflected by changes in behaviour. A substantial stress response occurs for 1-2 days following mulesing, and an acute phase response occurs for up to 7 days. Lambs consistently lose weight in the week after mulesing, and this has been associated with increased mortality rates under field conditions. Using these measures, it has been ascertained that mulesing poses a severe and sustained stressor for lambs, resulting in very poor welfare for a prolonged period of time. Pain relief can be provided for a short period (8-12 h) after the procedure, but a pain-free experience is not possible with current methods of pain relief. Alternative methods of breech modification involve the application of plastic occlusive clips or the intradermal delivery of sodium lauryl sulphate (SLS) to the breech. Both of these alternatives cause necrosis of the breech tissue without creating an open wound, and pose a much smaller challenge to welfare than surgical mulesing. Selection for sheep with low susceptibility to breech strike is considered to be the best long-term option, as this will provide a permanent, pain-free solution in which the sheep do not require any interventions. These changes will require time to implement, possibly 10-15 years, and alternative methods and management practices (such as those reviewed here) that provide protection must be used in the interim.

Full text

Lamb mulesing: impact on welfare and alternatives
Lauren E. Edwards
Address: Animal Welfare and Biodiversity Research Group, Department of Natural Sciences, Unitec Institute of Technology,
Carrington Road, Mt Albert, Private Bag 92025, Auckland, New Zealand.
Correspondence: Email: ledwards@unitec.ac.nz
Received: 11 June 2012
Accepted: 20 September 2012
doi: 10.1079/PAVSNNR20127061
The electronic version of this article is the definitive one. It is located here: http://www.cabi.org/cabreviews
gCAB International 2012 (Online ISSN 1749-8848)
Abstract
Mulesing is a surgical procedure that is routinely performed without pain relief on Merino and
Merino cross sheep to prevent flystrike in the breech region. Pain is apparent immediately
following the procedure and persists for at least 2–3 days, and possibly up to 2 weeks, as reflected
by changes in behaviour. A substantial stress response occurs for 1–2 days following mulesing, and
an acute phase response occurs for up to 7 days. Lambs consistently lose weight in the week after
mulesing, and this has been associated with increased mortality rates under field conditions. Using
these measures, it has been ascertained that mulesing poses a severe and sustained stressor for
lambs, resulting in very poor welfare for a prolonged period of time. Pain relief can be provided for
a short period (8–12 h) after the procedure, but a pain-free experience is not possible with current
methods of pain relief. Alternative methods of breech modification involve the application of
plastic occlusive clips or the intradermal delivery of sodium lauryl sulphate (SLS) to the breech.
Both of these alternatives cause necrosis of the breech tissue without creating an open wound,
and pose a much smaller challenge to welfare than surgical mulesing. Selection for sheep with low
susceptibility to breech strike is considered to be the best long-term option, as this will provide a
permanent, pain-free solution in which the sheep do not require any interventions. These changes
will require time to implement, possibly 10–15 years, and alternative methods and management
practices (such as those reviewed here) that provide protection must be used in the interim.
Keywords: mulesing, sheep welfare, clips, sodium lauryl sulphate, Tri-Solfen.
Review Methodology: The CAB Abstract database and the Australian Veterinary Journal were searched for the terms ‘mulesing’,
‘cutaneous myiasis and sheep’, ‘flystrike and sheep’ and ‘sodium lauryl sulphate and sheep’. The reference lists from the resulting
articles were also used as a source of relevant literature, and the website for Australian Wool Innovation Limited (www.wool.com) was
used to gain industry reports and newsletters.
Introduction
Mulesing is a surgical procedure that is routinely per-
formed on Merino and Merino cross sheep to reduce the
incidence of flystrike. Flystrike occurs when gravid female
blowflies, generally of the species Lucilia cuprina [1], lay
eggs in the moist fleece of a sheep, resulting in an infes-
tation of larvae (maggots) that feed on the sheep’s tissues.
During flystrike, sheep show obvious signs of distress such
as restlessness and biting of the affected area, as well as a
sustained physiological stress response that continues for
as long as the infestation is present [2–4], indicating
substantial compromise to the welfare of struck sheep. In
extreme cases when the sheep is not treated, this con-
dition results in mortality. Flystrike has been estimated to
cost the Australian wool industry $280 million per year
[5] and causes the death of 3 million sheep annually [6].
Current mortality rates are likely to be lower than this
1990 estimate due to the development of long-acting
insecticides such as dicyclanil and cyromazine; however,
the prevention of flystrike is still a high priority in terms of
both animal welfare and profitability for producers.
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A sheep becomes susceptible to flystrike when
the fleece becomes wet for prolonged periods, and the
odour of the microbial environment within the wet fleece
attracts gravid female blowflies [7]. Prolonged rainfall [6]
or urine staining can lead to persistently wet fleece, but it
is the accumulation of faecal matter around the perineum
(dags) that poses one of the greatest risk of flystrike in the
tail and breech area [8, 1]. Merino sheep and their crosses
are particularly susceptible to breech strike due to the
wrinkly nature of their skin. The wrinkles present around
the breech not only accumulate more dags and urine, but
also trap moisture for longer, creating an optimal envir-
onment for oviposition by the blowfly and promoting
larvae survival. The amount of wool cover surrounding
the perineum also influences the amount of dags and
urine that accumulate; however, it is the degree of breech
wrinkle and dagginess that are the main predisposing
factors for flystrike [8].
To combat breech strike, a surgical procedure called
mulesing was developed in 1931 by an Australian wool-
grower named John Mules [9, 10]. The procedure is
described as ‘the removal of wool-bearing skin from
the tail and breech area of the sheep’ and is performed on
Merino or Merino cross lambs between the ages of 2
and 12 weeks old [11], without analgesia or pre-operative
anaesthesia. As these wounds heal, the skin around the
breech is stretched, creating a bare, wrinkle-free area
around the breech and tail that is resistant to the accu-
mulation of urine and faeces [12]. Correct tail docking is
also an important component of managing breech strike,
as tails that are too short are associated with increased
dag accumulation and tail strike [1, 10, 13].
Despite the considerable pain and welfare compromise
that this procedure causes, mulesing remains a standard
component of Merino husbandry because of the high
efficacy of the procedure in combating breech strike.
Any viable alternative must offer clear welfare benefits,
not only at the time of mulesing, but also throughout
the animal’s lifetime in terms of flystrike protection.
This review will examine the impact of mulesing and the
current alternatives to mulesing on sheep welfare.
The Impact of Mulesing on Sheep Welfare
Animal welfare science uses two main approaches to
assess the welfare status of animals in response to a
stressor: the nature of the affective states that the
stressor elicits, such as fear and pain (inferred through
changes in behaviour and physiology), and the degree of
biological dysfunction that occurs in response to the
stressor, such as changes in physiology, health and fitness
parameters. In both respects, the magnitude of the
response and the duration of the response are used to
assess the severity of the welfare challenge. An integrated
approach that incorporates both affective states and
biological function as the assessment criteria is the
optimal method for assessing welfare, and this review will
address the indicators of both.
Impact on Affective States
The immediate and intense changes in behaviour and
physiology that occur following mulesing indicate that
this is a painful procedure. Fell and Shutt [14] reported
that neither mulesed nor sham-mulesed lambs vocalized
during the procedure, but that the mulesed lambs strug-
gled more. Plasma cortisol concentrations are elevated
approximately 70–200% above those of sham-mulesed
control lambs within 15 min of mulesing [14–16], and from
10 to 300% above by 30 min [17–21].
Shortly after mulesing, sheep assume the characteristic
‘statue standing’ response in which they stand with their
heads down and back arched for long periods. They also
make unsuccessful attempts to lie down [17, 18, 22]. This
behavioural inhibition appears to be an attempt by the
lambs to reduce movement of the damaged tissues
around the breech, and is strongly indicative of pain.
When the time budgets of mulesed lambs are compared
with those of control lambs, mulesed lambs spend a
greater portion of their time standing and less time lying
for up to 3 days following the treatment [14–18]. Mulesed
lambs also show stiff walking behaviour for 2 days after
treatment [14, 18] and in one study, gait score was
significantly poorer than that of controls at 18 days
post-treatment [15]. Mulesed lambs show an increase in
total abnormal behaviours, such as hunched standing, stiff
walking and failed attempts at lying, for 2 days following
mulesing [17, 18], and a reduction in feeding behaviour for
approximately 2 weeks [15, 17]. These studies provide
reasonably strong evidence that mulesed lambs undergo
an acute pain response indicated by severe behavioural
inhibition for 2 to 3 days following mulesing, with some
behavioural inhibition for up to 2 weeks following the
procedure that is likely to indicate pain.
In addition to pain, there is evidence that mulesing
results in increased avoidance of humans [14, 16], with
some indication that this response may apply to the
specific operators who performed the procedure [14].
This avoidance behaviour persists for 3–5 weeks after the
procedure, providing an indication of how aversive the
sheep perceive mulesing to be. Fear is an aversive affective
state that is detrimental to animal welfare, and while it
does not possess the same gravity as pain, it must be
acknowledged as a negative welfare outcome of mulesing.
Impacts on Biological Function
The biological dysfunction that occurs in response to
mulesing indicates a substantial and sustained challenge
to sheep welfare, based on measures of the general stress
response, acute phase response to tissue damage and
impact on fitness parameters.
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Following the initial surgical insult, plasma cortisol
concentrations show a biphasic response at 30 min and
12 h [20] or 24 h [14]. The first peak is a response to the
pain, fear and novelty, as described above, and the second
peak is related to the inflammatory response to the
tissue trauma incurred [23]. Cortisol remains significantly
elevated above that measured in control lambs for at
least 24 h [20, 21] and often 48 h or more [14–19]. The
neutrophil:lymphocyte (N:L) ratio is a commonly accep-
ted indicator of stress that is significantly elevated in
mulesed lambs and generally peaks at 24 h post-mulesing
[18–20]. From this information, it can be concluded that
the combined stressors involved in the mulesing proce-
dure and the subsequent acute phase response result in a
substantial stress response in lambs for at least 2 days.
Haptoglobin forms part of the acute phase response
and is used as an indicator of the severity of tissue damage
and inflammation. Following mulesing, haptoglobin con-
centrations peak on the second or third day after
mulesing and remain significantly elevated above controls
for 1 week [15, 17–20, 24]. Beta-endorphins are an
endogenous opioid released in response to emotional or
surgical stress [4] and have been shown to increase at
30 min and 12 h after mulesing [14, 17–20], although in
two of these studies the control lambs also showed
a similar increase in this protein [17, 19], presumably as
a result of the stress associated with handling.
Indicators of fitness in farmed species include measures
of survival and changes in bodyweight, rather than the rate
of reproduction, as farming practices often limit oppor-
tunities for reproduction in these species. One recent
study found that mulesed lambs had a 4% lower survival
rates than non-mulesed lambs at 90 days post-mulesing
[25]. The authors attributed the reduced survival rate to
the weight loss that occurred following mulesing, as body
weight and growth rates are strongly associated with
survival rates in lambs following weaning [26].
Most studies that measured changes in bodyweight
following mulesing have found a reduction in weight
during the first week. Lambs lost between 0.5 and 1.5 kg
during the week after mulesing [15, 16, 20, 24, 25] or
showed reduced average daily gains [17, 19, 21], and took
1 [17, 19, 20, 21] to 4 [15, 16, 24] weeks to recover. This
weight loss may be attributed to reduced feeding beha-
viour and reduced availability of resources for growth due
to healing. The wounds incurred by mulesing can take up
to 47 days to heal [12].
In conclusion, the literature shows that mulesing poses
a severe and sustained stressor for sheep that have
undergone this procedure, resulting in very poor welfare
for a prolonged period of time.
Alternatives to Current Mulesing Practice
For an alternative to surgical mulesing to be acceptable in
commercial use it must not only alleviate the acute impact
of mulesing on sheep welfare, but also protect the lifetime
welfare of the sheep by preventing breech strike. Various
alternatives to surgical mulesing had been investigated
prior to the anti-mulesing campaign in 2004, such as the
topical application of caustic chemicals, freezing the skin
of the breech, radiation treatment, light treatment and
intradermal injection of the enzyme collagenase to modify
the amount of wrinkle or wool cover present on the
breech [27]. The intradermal injection of cetrimide has
been the subject of a substantial amount of research.
However, this method of breech modification has not
been shown to offer welfare benefits over surgical
mulesing [12, 18, 19, 24] and none of these options have
been developed for commercial use by woolgrowers.
Only those methods that have been developed as viable
options for commercial use will be reviewed, as these
are the most relevant to the welfare of the Australian
flock. These methods can be categorized into: alternative
methods of breech modification; surgical mulesing with
pain relief; selection against flystrike susceptibility and
alternative management methods.
Alternative Methods of Breech Modification
Clips
Plastic occlusive clips that partially replicate the effects
of mulesing without creating an open wound became
commercially available in 2009 [5]. The loose skin on the
tail and breech is occluded through the clips, laterally
stretching the perineal and tail areas to reduce breech
wrinkle. The pressure from the clips causes ischaemic
necrosis and sloughing of the skin approximately
2–4 weeks after application without creating an open
wound [12, 25]. Alternately, the clips can be removed
after 4–6 days to allow reuse and avoid contaminating
paddocks with sloughed clips [28]
The behavioural indicators of pain were minimal in
lambs receiving the clips treatment, although only two
published studies have measured the behavioural
response of sheep to this procedure. During the 2 h
immediately following treatment, lambs that had received
the clips treatment spent more time standing with the
head down than control lambs [22]. In the following 21
days, the same lambs showed no other differences in
behaviour or gait compared with the control lambs [15].
The physiological stress response to the clips was sub-
stantially smaller in comparison with that of surgical
mulesing. The cortisol concentration of lambs receiving the
clips treatment was significantly greater than that of the
controls on the day of treatment only [15], compared with
1–2 days for mulesed lambs. The neutrophil:lymphocyte
ratio was significantly higher than that of the controls on the
day after treatment in one study [15] and for 5 days after
treatment in another [24]. In addition, the concentrations
of selected acute phase proteins showed a relatively mild
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Lauren E. Edwards 3

increase for approximately 1 week after treatment [15, 24].
This may be related to a lesser degree of tissue damage
occurring in comparison with surgical mulesing, or the fact
that the necrotizing tissue and its associated toxins were
isolated from the live tissue by the clips [19].
The fitness of lambs receiving the clips treatment
is substantially higher than that of mulesed lambs, as
measured by weight gain, survival rate and rate of
wound healing. The clips caused lamb growth to slow for
2–4 weeks after treatment [24, 25, 28], but did not
cause weight loss, as seen in mulesed lambs. In fact,
lambs receiving the clips treatment on-farm weighed sig-
nificantly more than mulesed lambs for 6 months post-
treatment [25]. The 4% increase in survival rates of the
clipped lambs compared with the mulesed lambs in
this study was attributed to the increased bodyweight of
the clipped lambs following treatment [25]. In a study
comparing the rates of wound healing, the wound beds
created by clips were completely re-epithelialized by 32
days post-treatment, compared with 47 days in surgically
mulesed lambs [12].
In conclusion, clips had a small to moderate impact on
acute welfare, and all studies that compared clips against
mulesing invariably concluded that clips provided sub-
stantial benefits over mulesing in the short term. The
behavioural indicators of pain were briefer and of a
smaller magnitude than those induced by mulesing (1 day
clips versus 2–3 days mules), as was the cortisol response
(1 day clips versus 1–2 days mules). The acute phase
response to tissue damage was minimal, and while growth
was slowed for a short period after treatment the clipped
lambs did not lose weight. Clipped lambs also had higher
survival rates than mulesed lambs. Based on these
welfare indicators, the use of plastic clips appears to offer
a more humane method of breech modification than
mulesing.
Despite these welfare benefits, recent research has
indicated that the use of plastic clips cannot provide the
same degree of protection from breech strike as surgical
mulesing [29]. Larsen et al. [29] reported that the inci-
dence of breech strike was significantly higher for clipped
sheep in comparison with surgically mulesed sheep (7.7
and 1.1%, respectively). While further research into the
lifetime effectiveness of the plastic clips in preventing
breech strike is required, it currently appears that if the
plastic clips are to be used, then they must be supported
by additional protective measures, such as the use of
insecticides [29].
Intradermal Sodium Lauryl Sulphate (SLS)
A second method for modifying the breech involves
intradermal injection of SLS into the skin surrounding the
breech and on the tail using a needle-less applicator. The
applicator forces the SLS compound through the dermis
causing immediate (2 min) local necrosis of the tissues,
followed by swelling, eschar formation and complete
sloughing by 28 days post-treatment [30]. As the wound
heals it causes contraction of the skin on the perineum
and tail, reducing wrinkle and increasing the size of the
bare area. This method is currently being developed for
commercial use [5].
The behaviour of lambs receiving intradermal injections
of SLS was indicative of discomfort during the first
1–2 days after application. During the 2 h immediately
following injections, lambs treated with SLS showed
increased kneeling behaviour and spent longer standing in
a hunched posture than controls [17, 22]. There was also
a tendency for an increase in abnormal behaviours on the
day of treatment, as well as more total time standing
and less time lying than the control lambs during the 48 h
post-treatment [17]. Another study reported a reduction
in feeding compared with controls on the day after
treatment [15]. Lee and Rothwell [30] reported no
behavioural change in lambs receiving SLS on the day after
treatment; however, these authors were looking for
conspicuous pain behaviours (restlessness, biting/rubbing
the area, inhibited movement) and did not measure time
budgets.
The physiology of lambs receiving intradermal SLS
indicates a moderate stress response to the procedure
for 1–2 days. Cortisol was significantly elevated by 15 min
post treatment [15], and remained elevated until the day
after treatment [15, 17]. The cortisol concentrations
were comparable with that of mulesed lambs at both 12 h
post-treatment and on the following day [15, 17]. In
addition, the N:L ratio and the white cell counts were
both significantly elevated above controls on the day after
treatment [15, 17]; and again on day 4 in the case of the
white blood cell counts, indicating an immunological
response to the tissue damage incurred. Haptoglobin
concentrations were elevated at 1–2 days after the pro-
cedure, and remained elevated for approximately 4 days
[15, 17].
Little information has been published on the effects of
intradermal SLS on the fitness of the animals, but there
was no impact on growth following treatment for 25 [15]
or 42 days [17] and this effect would appear to be mini-
mal. There is also a paucity of data relating to the lifetime
efficacy of this procedure in protecting sheep from breech
strike.
In conclusion, the use of intradermal SLS provides a
promising alternative to surgical mulesing from an animal
welfare perspective. Behavioural indicators of pain were
present for 1–2 days, compared with 2–3 days in mulesing.
The cortisol response was comparable between lambs
receiving SLS and mulesing, indicating a similar stress
response. However, the acute phase response to the SLS
treatment was approximately half that of the mulesing
treatments indicating a reduced amount of tissue damage
incurred. In addition, SLS appears to have little impact on
growth of lambs. Based on these welfare indicators,
intradermal SLS appears to offer a more humane method
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of breech modification than mulesing, but still results in a
moderate welfare challenge.
Surgical Mulesing with Pain Relief
The pain experienced by sheep during mulesing is the
greatest welfare concern resulting from this procedure,
and an immediate solution to this problem would at first
appear to be the use of pain relief. However, while some
relief can be provided immediately following the mulesing
procedure, providing total pain relief for a sufficient
duration following mulesing is a complex problem that
cannot be wholly dealt with using current pain relief
methods [23].
The mulesing procedure results in two distinct pain
responses. The first is the immediate response to the
surgical incisions, tissue removal and the resulting open
wound bed. The second response relates to the inflam-
mation of the tissues that occurs during the acute phase
response to tissue trauma [23, 31]. As discussed above,
this pain is evident during the first 2–3 days following
mulesing, and may persist for at least 2 weeks.
The large area of tissue involved in the mulesing pro-
cedure makes the pre-administration of local anaesthetic
to the breech impractical [21, 23]. A topical anaesthetic
(Tri-Solfen) has been developed for commercial use
(Bayer Industries), which consists of a gel containing long-
acting local anaesthetics combined with adrenaline and
an antiseptic that is sprayed directly onto the open wound
immediately post-mulesing [32]. This topical anaesthetic
was made commercially available in 2005 [33], and its
use has been steadily increasing since 2010 (http://www.
awex.com.au/market-information/mulesing-status.html).
Tri-Solfen has been shown to improve wound healing
rates, reduce the behavioural response to direct stimu-
lation of the open wound bed and surrounding skin for
4–8 h following mulesing, and reduce the incidence of
abnormal postures and gait during the 4-h observation
period following mulesing [32]. A study by Paull et al. [21]
found that treating mulesed lambs with Tri-Solfen had
little effect on behaviour during the 4 h following mulesing,
although the duration of hunched standing was reduced
and the duration of lying behaviour was increased in
comparison with that of mulesed lambs. There were very
few behavioural differences between the mulesed lambs
and those treated with Tri-Solfen during the subsequent
4–12 h period, and the authors described the effect of
Tri-Solfen as ‘rather modest’ [21]. It should be noted that
a placebo gel containing only the adrenaline and antiseptic
produced a behavioural response that was intermediate
to that of the Tri-Solfen and control treatments, indicating
that at least part of the relief could be attributed to the gel
barrier covering the open wound, rather than the action
of the local anaesthetics alone [32].
Non-steroidal anti-inflammatories (NSAIDs) have been
investigated as longer-lasting pain relief options [31].
The use of NSAIDs alone did not reduce the behavioural
or physiological response to surgical mulesing [20, 21].
However, when the NSAID carprofen was combined with
the topical anaesthetic Tri-Solfen, the behavioural and
physiological pain responses of the treated lambs did not
differ from control lambs for 6 h following mulesing, and
showed only mild differences from controls at 8–12 h
[21]. Despite this short-term pain relief, the cortisol
response of the treated lambs matched that of the
mulesed lambs by 24 h, and both mulesed and treated
lambs lost weight following mulesing, indicating that the
analgesic benefits of the NSAID and Tri-Solfen combina-
tion could not fully address the welfare challenge imposed
by surgical mulesing. The re-administration of pain relief at
regular intervals following mulesing has not been investi-
gated due to the recommendation that mulesed lambs
should not be handled in the 4 weeks following mulesing
to aid wound healing [11].
In conclusion, providing pain relief following surgical
mulesing does offer benefits to welfare in the short-term
(up to 12 h), and any reduction in the severity of pain
experienced by lambs is an improvement on traditional
surgical mulesing [23]. However, the pain of the surgical
incisions and tissue removal is still experienced by the
lambs, as is the longer-term pain that is present when the
analgesics wear off, and there are no longer-term studies
assessing the impact of pain relief on welfare and fitness
parameters. In addition, no research has been directed at
readministering pain relief options and what impact this
may have on wound healing rates, but Fisher [23] warns
against developments that may lead to a dependence
on pain relief measures rather than moving towards a
permanent solution to the mulesing issue through genetic
selection.
Selection against Flystrike Susceptibility
The traits that have the greatest impact on susceptibility
to breech strike (breech wrinkle, breech cover and
dags) are found to vary naturally within the Australian
Merino population, and are moderate to highly heritable
[5, 34–37]. In addition, whiter fleece is associated with
decreased strike susceptibility in areas with summer
rainfall [5]. The heritability of these traits offers the
Australian wool industry the opportunity to select
for sheep with low breech wrinkle, bare breeches,
whiter wool and less dags, thus removing the need for
mulesing.
A genetic solution to the mulesing issue is an attractive
option, as it offers a permanent, pain-free method of
combating breech strike. However, it is not an immediate
solution for the wool industry. The traits associated with
strike susceptibility are also associated to varying degrees
with fleece quality, and direct selection against these
could result in an unacceptable reduction in productivity
[34, 38]. Breech wrinkle is of particular concern,
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Lauren E. Edwards 5

as wrinkle score is correlated unfavourably with both
fleece weight and fibre diameter [34, 38]. This issue is
overcome by using a selection index that incorporates
both strike susceptibility and production traits as criteria
for selecting breeding stock. A selection index can
improve breech morphology while limiting the impact on
production traits, but markedly increases the amount of
time taken to achieve selection goals. Edwards et al. [39]
estimate that breech bareness (measured on a scale of
1–5), derived from a rare mutation, could be reduced by
0.2 units/year, and that it would take 10–15 years to
obtain an average flock score of one (completely bare).
This trait was correlated with lower dagginess [40] and a
reduced incidence of flystrike [41] in New Zealand breeds
of sheep. Brown et al. [34] estimate that breech wrinkle
score (on a scale of 1–5) could be reduced by 0.4–
0.9 units over 10 years, and a reduction in breech wrinkle
score of 0.5 units/10 years was recommended by Richards
and Atkins [38] if financial losses were to be minimized to
20–30%. Recent unpublished results of a breeding pro-
gramme have determined that a breech wrinkle score,
breech cover score and dag score of 2 (on a scale of
1–5) will provide the same degree of protection from
strike as surgical mulesing [42]. Thus, the average score
of the flock for each of these traits at the start of the
selection programme combined with the strength of
the selection pressure will determine the length of time
required to reduce the risk of breech strike to an
acceptable level.
Another area of genetic research involves selection for
improved parasite resistance. The presence of dags and
scouring is often the result of intestinal worm burdens [2],
and resistance to these parasites is heritable [43]. Sheep
also show variation in the attractiveness of their fleece to
gravid blowflies [44], presumably because of variation in
fleece characteristics and the microbial environment
of the fleece. In addition, variation in the ability of the
host’s immune response to inhibit larval growth has
been observed [44]. The effects of fleece characteristics
and the immune response to both worm burdens and
fly strike may offer further opportunities for selecting
improved strike resistance in sheep. It may also help
researchers understand the observed variation in breech
strike rates among research animals with similar breech
morphology [45].
Selection against susceptibility to breech strike is
recognized as the optimal solution to the mulesing issue
[23, 35, 46]. The selection process does not negatively
impact on the welfare of the sheep, nor do the breech
modifications being selected for. In fact, there is some
evidence that selection for improved breech morphology
is also associated with improved body weight and possibly
lamb survival [42], suggesting welfare and production
improvements above and beyond those related to
reducing the need for surgical mulesing. However, the
selection process is a lengthy one, and protection from
breech strike is required in the interim.
Alternative Management Methods
While mulesing provides the most effective protection
against breech strike, alternative management methods
that do not involve breech modification are also
available. These involve reducing the attractiveness
of the fleece to gravid blowflies through the use of
insecticides, optimal timing of shearing and crutching
and management of scouring [8, 46]. Increasing the
frequency of inspections is also required during
periods of high fly pressure to minimize the impact
of strike on the welfare and productivity of struck
animals.
The life cycle of the blowfly L. cuprina means that
adult flies are only present during the warmer months,
and therefore flystrike is a seasonal problem for pro-
ducers. In addition, the risk of breech strike increases
with increasing fleece length [8]. Thus, it is beneficial to
shear or crutch sheep at the beginning of the warmer
months to reduce the fleece length surrounding the
breech, minimizing the availability of oviposition sites for
gravid female blowflies. Crutching is an easier proce-
dure than shearing to time correctly, and provides
protection from breech strike for approximately
2 months [8].
Insecticides can be applied to the wool of the breech
area to deter flies, and these chemicals can be very
effective. For example, dicyclanil provided effective pro-
tection from flystrike in unmulesed sheep for approxi-
mately 5 months [47]. However, the heavy reliance on
insecticides is discouraged, as this practice has previously
led to chemical resistance in blowflies during the 1950s
and 1960 s [10].
Improved management of scouring will help to re-
duce the risk of flystrike by decreasing the dagginess
of the breech area. Typically, this will involve improved
management of internal parasite burdens through drench-
ing, correct pasture management and selecting against
dagginess in breeding stock [8, 46].
The alternative management options briefly described
here all require additional inputs when compared with
mulesing. Crutching, jetting insecticides and drenching all
involve additional costs and labour, and these are
ongoing costs that need to be repeated every year. In
relation to the welfare implications of this approach, no
research has been conducted on the cumulative effects
of the additional handling involved on the welfare of
sheep. In addition, the risk of breech strike must be
included in these assessments: any increase in the risk
of flystrike over the lifetime of the sheep will detract
from the welfare benefits obtained by not mulesing.
The attitudes of farmers to these husbandry practices
are positive, but they are viewed as complementary
rather than primary methods of controlling breech
strike [48], and it appears unlikely that breech strike will
be successfully managed without any form of breech
modification.
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6 CAB Reviews

Conclusion
From this review of the literature, it is evident that
mulesing poses a substantial and sustained challenge to
sheep welfare. Alternative methods of protecting sheep
from breech strike involve non-surgical methods of
breech modification (clips or intradermal SLS), the
provision of pain relief during surgical mulesing, selection
for low susceptibility sheep, and improved management
and monitoring of risk factors in the flock. The efficacy of
the plastic clips and intradermal SLS in providing lifetime
protection from breech strike have not yet been com-
pared with that of surgical mulesing, but warrant further
investigation.
Selection of sheep with low susceptibility to breech
strike is considered to be the best long-term option, as
this will provide a permanent, pain-free solution in which
the sheep do not require any interventions. These chan-
ges will require time to implement, possibly 10–15 years,
and alternative measures (such as those reviewed here)
that provide protection must be used in the interim.
Acknowledgements
The author thanks Dr Adele Arnold for her helpful
comments on the manuscript.
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